Dp hdcp version converter

ABSTRACT

A DisplayPort (DP) High-bandwidth Digital Content Protection (HDCP) version converter that converts an HDCP content protection version from input to output includes a receiver and a transmitter. The receiver receives a serial bit stream transmitted from an upstream device, and decrypts link symbols of the received serial bit stream by use of a decryption unit. The transmitter encrypts, by use of an encryption unit, the link symbols decrypted by the receiver, and converts the encrypted link symbols into a serial bit stream and transmits the serial bit stream to a downstream device. The receiver and the transmitter have the same link configuration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromU.S. application Ser. No. 61/972,923, filed Mar. 31, 2014, the entirecontents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to technology for converting aHigh-bandwidth Digital Content Protection (HDCP) content protectionversion.

BACKGROUND ART

DisplayPort (see Non-patent Document 1) is known as a digital interfacestandard. Meanwhile, HDCP is known as technology for protecting content.HDCP specifications can be obtained from www.digital-cp.com.

PRIOR ART DOCUMENT Non-Patent Document

-   Non-patent Document 1: “DisplayPort Standard” version 1.2a, May 23,    2012, VESA

SUMMARY OF INVENTION Problems to be Solved by the Invention

When a device whose input and output comply with DisplayPort(hereinafter, also referred to as DP) converts an HDCP contentprotection version of an incoming stream, and outputs the stream,simplification of the conversion is desired. Some examples of theconversion arc from HDCP Ver.1.3 (HDCP1.3) content protection to HDCPVer.2.2 (HDCP2.2) content protection, and vice versa (that is, fromHDCP2.2 content protection to HDCP1.3 content protection).

The present invention aims to provide technology enabling simplificationof conversion of an HDCP content protection version.

Means for Solving the Problems

A DisplayPort (DP) High-bandwidth Digital Content Protection (HDCP)version converter that converts an HDCP content protection version frominput to output includes a receiver and a transmitter. The receiverreceives a serial bit stream transmitted from an upstream device, anddecrypts link symbols of the received serial bit stream by use of adecryption unit. The transmitter encrypts, by use of an encryption unit,the link symbols decrypted by the receiver, and converts the encryptedlink symbols into a serial bit stream and transmits the serial bitstream to a downstream device. The receiver and the transmitter have thesame link configuration.

Effects of the Invention

Conversion of an HDCP content protection version is simplified.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows configuration of an image display system 1.

FIG. 2 shows processes in a DP MST Source device and in a DP SST Sinkdevice.

FIG. 3 shows processes in a DP MST Branch device.

FIG. 4 shows processes in a DP HDCP converter.

DESCRIPTION OF EMBODIMENT

The present disclosure is applied to a DisplayPort(DP)-in, DP-out devicethat converts an HDCP content protection version from input to output.The present disclosure enables simplification of a DP HDCP versionconverter supporting Multi Stream Transport (MST) transport format as 1)it allows for a converter without circuitry for either regeneratingstreams or routing multiple streams, and also as 2) insertion of theconverter does not add to MST topology cascade levels.

Details on DisplayPort and MST transport format/topology, and howselective encryption among multiple streams is supported across the MSTtopology are described in Non-patent Document 1. Non-patent Document 1is hereinafter also referred to as DP1.2a Standard.

FIG. 1 shows configuration of an image display system 1 including a DPHDCP version converter 3 (hereinafter, also simply referred to as aconverter 3) according to the present embodiment. FIG. 1 shows anexample of DP MST topology with the DP HDCP version converter 3.

As shown in FIG. 1, the image display system 1 includes a DP MST Sourcedevice 2 (hereinafter, also simply referred to as a Source device 2),the converter 3, DP MST Branch devices 4 a and 4 b (hereinafter, alsosimply referred to as Branch devices 4 a and 4 b), and DP Single StreamTransport (SST) Sink devices 5 a, 5 b, and 5 c (hereinafter, also simplyreferred to as Sink devices 5 a, 5 b, and 5 c). In the image displaysystem 1, images generated by the Source device 2 are displayed in theSink devices 5 a, 5 b, and 5 c.

The Source device 2, the converter 3, the Branch devices 4 a and 4 b,and the Sink devices 5 a, 5 b, and 5 c each comply with DP. The Sourcedevice 2, the converter 3, and the Branch devices 4 a and 4 b eachsupport MST. The converter 3 supports not only MST but also SST. TheSink devices 5 a, 5 b, and 5 c each support SST.

The Source device 2 is an upstream device of the converter 3, and isconnected to the converter 3 via an upstream link. The Source device 2generates a serial bit stream protected by HDCP1.3, and outputs theserial bit stream to the converter 3 through use of the upstream link,for example.

The converter 3 converts the HDCP content protection version of theserial bit stream output from the Source device 2 from HDCP1.3 toHDCP2.2, for example, and outputs the serial bit stream protected byHDCP2.2. The converter 3 includes an upstream facing port (UFP) receiver30 that receives the serial bit stream protected by HDCP1.3 from theSource device 2, and a downstream facing port (DFP) transmitter 31 thattransmits the serial bit stream protected by HDCP2.2. The UFP receiver30 and the DFP transmitter 31 are described in detail later.

The Branch device 4 a is a downstream device of the converter 3, and isconnected to the converter 3 via a downstream link. The Branch device 4a separates the serial bit stream input from the converter 3 via thedownstream link into two serial bit streams, and outputs the serial bitstreams. The Branch device 4 b separates one of the serial bit streamsoutput from the Branch device 4 a into two serial bit streams, andoutputs the serial bit streams. The Branch devices 4 a and 4 b eachcorrespond to HDCP2.2.

The Sink device 5 a displays an image based on the other one of theserial bit streams output from the Branch device 4 a. The Sink device 5b displays an image based on one of the serial bit streams output fromthe Branch device 4 b. The Sink device 5 c displays an image based onthe other one of the serial bit streams output from the Branch device 4b. The Sink devices 5 a, 5 b, and 5 c each correspond to HDCP2.2.

Hereinafter, the Branch devices 4 a and 4 b are each referred to as aBranch device 4 when there is no particular need to distinguish betweenthem. Similarly, the Sink devices 5 a, 5 b, and 5 c are each referred toas a Sink device 5 when there is no particular need to distinguish amongthem.

<AV Stream Data Path from Source to Sink>

FIG. 2 is a layered diagram of an audio visual (AV) stream data pathfrom a stream source to a stream sink via a high-speed serial link. FIG.2 shows operation of a DFP transmitter of the Source device 2 on theleft side, and shows operation of an UFP receiver of the Sink device 5on the right side. In the example of FIG. 2, a serial bit stream outputfrom the Source device 2 is directly input into the Sink device 5, andthe Source device 2 and the Sink device 5 correspond to HDCP in the sameversion.

The DFP transmitter of the Source device 2 generates original AV streamdata at a stream layer 200. The DFP transmitter then maps the generatedAV stream data to link symbols at a link layer 201. The DFP transmitterthen encrypts, at an HDCP content protection layer 202, the link symbolsto which the AV stream data is mapped. Specifically, the DFP transmittercalculates XOR (exclusive or) of the link symbols and a cipher value toencrypt the link symbols. Next, at a PHY (physical) digital layer 203, ascrambler of the DFP transmitter scrambles the encrypted link symbols,and an encoder of the DFP transmitter performs channel coding(ANSI8B10B) on the scrambled link symbols. Then, at a PHY analog layer204, a serializer of the DFP transmitter converts the link symbolsprocessed at the PHY digital layer 203 into a serial bit stream, and aserial bit driver of the DFP transmitter outputs the generated serialbit stream. The serial bit stream transmitted from the DFP transmitterof the Source device 2 is input into the Sink device 5 through ahigh-speed serial main link between the Source device 2 and the Sinkdevice 5.

In the UFP receiver of the Sink device 5, at a PHY analog layer 504, aserial bit receiver receives the serial bit stream from the Sourcedevice 2, and a de-serializer converts the received serial bit streaminto a parallel signal. Next, in the UFP receiver, at a PHY digitallayer 503, a decoder decodes the parallel signal generated at the PHYanalog layer 504, and a de-scrambler descrambles a signal obtainedthrough decoding. As a result, link symbols that are encrypted(encrypted link symbols) are obtained. The UFP receiver then decrypts,at an HDCP content protection layer 502, the encrypted link symbolsobtained at the PHY digital layer 503. Specifically, the UFP receivercalculates XOR of the encrypted link symbols and the cipher value todecrypt the encrypted link symbols. The UFP receiver then maps thedecrypted link symbols to stream data, and regenerates a stream timingat a link layer 501. Framing/stuffing symbols are herein removed fromthe decrypted link symbols, and the stream data is generated based onthe remaining link symbols. An AV stream clock (i.e., a video pixelclock and an audio clock) is not regenerated. The UFP receiver thenregenerates, at a stream layer 500, the original AV stream data based onthe stream data generated and the stream timing regenerated at the linklayer 501. Furthermore, the AV stream clock is regenerated at the streamlayer 500. In the Sink device 5, based on the regenerated AV stream dataand AV stream clock, a video is displayed, and an audio according to thevideo is output. As a result, the video and audio generated by theSource device 2 are reproduced in the Sink device 5.

As described above, the HDCP content protection layer resides betweenthe link layer (layer handling mapping between AV stream data and linksymbols) and the PHY digital layer (layer handling conversion betweenlink symbols and channel coding characters that are ANSI8B10B channelcoding characters for DP link).

<Branch Device>

DP1.2a Standard defines a DP-in, DP-out MST Branch device that routesmultiple streams from input port(s) to output port(s) withoutregenerating original audio visual (AV) streams. The MST specificationsof DP1.2a Standard allow the lane counts and link rates to be setindependently on the input port(s) and the output port(s) of the MSTBranch device that remaps incoming link symbols on its output port(s).

FIG. 3 is a layered diagram within the Branch device 4. FIG. 3 showsoperation of an UFP receiver of the Branch device 4 on the left side,and shows operation of a DFP transmitter of the Branch device 4 on theright side.

The Branch device 4 routes multiple streams from the input port(s) tothe output port(s) via multi-stream routing circuitry withoutregenerating original AV streams. In the Branch device 4, the linkconfiguration (that is, the combination of link rate and lane count) ofthe DFP transmitter may be different from that of the UFP receiver.

As shown in FIG. 3, in the UFP receiver of the Branch device 4, at a PHYanalog layer 404, a serial bit receiver receives a serial bit streamoutput from a DFP transmitter of an upstream device of the Branch device4, and a de-serializer converts the received serial bit stream into aparallel signal. Next, in the UFP receiver, at a PHY digital layer 403,a decoder decodes the parallel signal generated at the PHY analog layer404, and a de-scrambler descrambles a signal obtained through decoding.As a result, encrypted link symbols are obtained. The UFP receiver thendecrypts, at an HDCP decryption layer (HDCP content protection layer)402, the encrypted link symbols obtained at the PHY digital layer 403according to HDCP2.2. The UFP receiver calculates XOR of the encryptedlink symbols and the cipher value to decrypt the encrypted link symbols.The UFP receiver then maps the decrypted link symbols to stream data,and regenerates a stream timing at a link layer 401.

The stream data generated at the link layer 401 is forwarded throughmulti-stream routing circuitry 410 to the DFP transmitter of the Branchdevice 4 based on the regenerated stream timing. Although a single DFPtransmitter is shown in FIG. 3, the branch device 4 is provided withmultiple DFP transmitters. In a case where multiple stream data piecesare generated at the link layer 401, the multi-stream routing circuitry410 routes each of incoming multiple stream data pieces to anappropriate DFP transmitter.

The DFP transmitter of the Branch device 4 maps, at a link layer 421,the stream data from the multi-stream routing circuitry 410 to linksymbols. The DFP transmitter then encrypts the link symbols according toHDCP2.2 at an HDCP encryption layer (HDCP content protection layer) 422.The DFP transmitter calculates XOR of the link symbols and the ciphervalue to encrypt the link symbols. Next, at a PHY (physical) digitallayer 423, a scrambler of the DFP transmitter scrambles the encryptedlink symbols, and an encoder of the DFP transmitter performs channelcoding on the scrambled link symbols. Then, at a PHY analog layer 424, aserializer of the DFP transmitter converts the link symbols processed atthe PHY digital layer 423 into a serial bit stream, and a serial bitdriver of the DFP transmitter outputs the generated serial bit stream.The serial bit stream transmitted from the DFP transmitter of the Branchdevice 4 is received by a UFP receiver of a downstream device of theBranch device 4.

As described above, since original AV streams are not regenerated in theBranch device 4, no stream layer is necessary. In FIG. 3, a frameshowing the unnecessary stream layer is indicated in a dashed line.

<Converter>

FIG. 4 is a layered diagram of the converter 3. In the converter 3according to the present embodiment, the same link configuration isapplied to the UFP receiver 30 and the DFP transmitter 31. Thiseliminates the need for remapping of the link symbols between the UFPreceiver 30 and the DFP transmitter 31. In the present embodiment, bylimiting each of the number of physical input ports and the number ofphysical output ports of the converter 3 to one and by causing theconverter 3 to have the same lane count and link rate between the inputport and the output port, the need for the converter 3 to perform linksymbol remapping is eliminated.

As shown in FIG. 4, in the UFP receiver 30 of the converter 3, at a PHYanalog layer 304, a serial bit receiver receives a serial bit streamoutput from a DFP transmitter of an upstream device (the Source device 2in the example of FIG. 1) of the converter 3, and a de-serializerconverts the received serial bit stream into a parallel signal.

Next, in the UFP receiver 30, at a PHY digital layer 303, a decoderdecodes the parallel signal generated at the PHY analog layer 304, and ade-scrambler descrambles a signal obtained through decoding. As aresult, encrypted link symbols are obtained.

The UFP receiver 30 then decrypts, at an HDCP decryption layer 302, theencrypted link symbols obtained at the PHY digital layer 303 accordingto HDCP1.3. The UFP receiver 30 calculates XOR of the encrypted linksymbols and the cipher value to decrypt the encrypted link symbols.

In the UFP receiver 30, an HDCP decryption block that performs theprocess at the HDCP decryption layer 302 decrypts the incoming encryptedlink symbols (upstream AV stream link symbols) without knowing what eachlink symbol represents, and forwards the decrypted link symbols (rawlink symbols) to an HDCP encryption block of the DFP transmitter 31along with an encryption enable control signal (ENCRYPT_EN signal) andan XOR enable control signal (XOR_EN signal).

Furthermore, if an HDCP version of a downstream link does not meet acontent security level for certain stream data specified by a securityengine of a stream source (the Source device 2), the converter 3 cannotforward the certain stream data to a downstream device. The HDCPdecryption block of the UFP receiver 30 thus replaces link symbol(s) ofthe certain stream data from an upstream device with filler symbol(s)according to the MST specifications of DP1.2a Standard. The HDCPdecryption block de-asserts an XOR_EN signal for these filler symbols.

The HDCP encryption block of the DFP transmitter 31 enables a cipheralgorithm engine for HDCP encryption when the ENCRYPT_EN signal isasserted at an HDCP encryption layer 312. The HDCP encryption blockcalculates XOR of the link symbols (AV stream link symbols) from theHDCP decryption block and the cipher value generated by the HDCPencryption block by using the cipher algorithm engine each time theXOR_EN signal is asserted when the ENCRYPT_EN signal is asserted.

In case of HDCP with the MST transport format, the Source device 2upstream of the converter 3 may choose to encrypt only a certain streamindicated in an Encryption Configuration Field (ECF) of an MST linkframe. The ECF indicates a time slot, within a 64-time-slot Multi-streamtransport Packet (MTP) encryption, to be enabled (that is, subjected toXOR with the cipher value). It is the responsibility of the HDCPdecryption block of the converter 3 to assert/de-assert the XOR ENsignal to the HDCP encryption block according to a value of the ECF ofan incoming serial bit stream in the MST transport format. That is tosay, the HDCP decryption block of the UFP receiver 30 asserts, accordingto the value of the ECF of the serial bit stream input into the UFPreceiver 30, the XOR EN signal forwarded to the HDCP encryption blockalong with the link symbols of the stream to be encrypted.

At a PHY (physical) digital layer 313, the link symbols processed by theHDCP decryption block of the DFP transmitter 31 are scrambled by ascrambler of the DFP transmitter 31, and then undergo channel coding byan encoder of the DFP transmitter 31.

Then, at a PHY analog layer 314, a serializer of the DFP transmitter 31converts the link symbols processed at the PHY digital layer 313 into aserial bit stream, and a serial bit driver of the DFP transmitter 31outputs the generated serial bit stream. The serial bit streamtransmitted from the DFP transmitter 31 of the converter 3 is receivedby a UFP receiver of a downstream device (the Branch device 4 a in theexample of FIG. 1) of the converter 3.

In the present embodiment, the UFP receiver 30 and the DFP transmitter31 of the converter 3 are each configured by analog circuitry anddigital circuitry, for example. The PHY analog layer 304 and the PHYanalog layer 314 are each configured by analog circuitry. The PHYdigital layer 303, the HDCP decryption layer 302, the HDCP encryptionlayer 312, and the PHY digital layer 313 are each configured by digitalcircuitry. The PHY analog layer 304, the PHY digital layer 303, the HDCPdecryption layer 302, the HDCP encryption layer 312, the PHY digitallayer 313, and the PHY analog layer 314 can respectively be referred toas analog receiving circuitry 304, digital processing circuitry 303,decryption circuitry 302, encryption circuitry 312, digital processingcircuitry 313, and analog transmitting circuitry 314. The UFP receiver30 and the DFP transmitter 31 are each configured by hardware circuitrythat does not require software to achieve its functions.

As described above, since original AV streams are not regenerated in theconverter 3, no stream layer is necessary. In addition, the same linkconfiguration (lane count and link rate) is applied to the UFP receiver30 and the DFP transmitter 31 in the converter 3. Herein, mapping ofstream data to link symbols depends on the lane count, and insertion ofstuffing symbols depends on a ratio of a link bandwidth to an AV streambandwidth. Therefore, by applying the same link configuration (lanecount and link rate) to the UFP receiver 30 and the DFP transmitter 31,remapping of the link symbols is unnecessary. This eliminates the needfor circuitry corresponding to the multi-stream routing circuitry 410 ofthe Branch device 4 as well as the need for the link layer in theconverter 3. Conversion of the HDCP content protection version can thusbe simplified. As a result, the converter 3 can be simplified. In FIG.4, frames showing the unnecessary stream layer and link layers areindicated in dashed lines.

<AUX Transactions>

The Source device 2 (see FIG. 1) initiates, according to DP 1.2aStandard, various AUX transactions, for example, including:

-   -   various message transactions for discovering the topology,        reading the capabilities of downstream Sink devices, etc.;    -   AUX transactions for link management such as link training and        link maintenance;    -   AUX transactions for HDCP authentication and key exchange; and    -   AUX transactions for implementation-specific purposes.

Various AUX transactions initiated by the Source device 2 are forwardedto the converter 3. In the present embodiment, the converter 3 forwardsall AUX transactions except for those for link management and for HDCPauthentication and key exchange to the downstream device. The converter3 thereby avoids adding to the MST topology cascade levels. In otherwords, the converter 3 does not add to the MST topology cascade levelsby forwarding all sideband channel transactions (AUX transactions overDP link) except for those for link management and for HDCPauthentication and key exchange. Therefore, in a case where the Branchdevice is assumed to be able to cascade up to seven devices in the DPspecifications, for example, the Branch device can cascade up to sevendevices even when there is the converter 3. In order to determinewhether to forward or consume the current AUX transaction, the converter3 checks a command and an address of the AUX transaction. Determinationon whether to forward or consume the AUX transaction may be made byhardware logic or firmware. AUX transaction flow control specified in DP1.2a Standard may be used by the converter 3 as needed.

As described above, the present embodiment discloses the device and themethod for simplification of the DP HDCP version converter supportingnot only SST transport format but also MST transport format. Thedisclosed device and method allow for HDCP content encryption ofmultiple streams transported with MST transport format without requiringmulti-stream routing circuitry. Furthermore, the disclosed device andmethod allow the DP HDCP version converter to be added to MST topologywithout adding to the MST topology cascade levels.

The disclosed device and method set the link rate and lane count of thedownstream link to be the same as those of the upstream link, andfurther forwards the link symbols from the UFP receiver to the DFPtransmitter at the HDCP content protection layer that handles HDCPencryption and decryption, instead of the link layer that handlesmapping between the link symbols and the AV stream or the stream layer.The method for setting the link rate and lane count of the downstreamlink to be the same as those of the upstream link is described for anSST Branch device (that is, a PHY (physical) layer repeater) in DP1.2aStandard, but the DP HDCP version converter can be in the MST transportformat including selective encryption among multiple AV streams. That isto say, the DP HDCP version converter can transport multiple AV streamsincluding an encrypted AV stream and an unencrypted AV stream.

In the disclosed device and method, the HDCP decryption block of the DPHDCP version converter forwards the decrypted AV stream link symbols tothe HDCP encryption block, along with the encryption enable controlsignal (ENCRYT_EN signal) and the XOR enable control signal (XOR_ENsignal). The decryption block asserts/de-asserts the XOR_EN signal basedon whether the link symbols need to be encrypted. For the MST case,determination on whether the link symbols are encrypted/unencrypted alsorequires interpretation, by the decryption block, of the ECF field of anupstream MST link frame according to DP1.2a Standard.

Furthermore, the HDCP decryption block of the UFP receiver replaces thelink symbols of certain stream data from the upstream device with fillersymbols according to the MST specifications of DP1.2a Standard if theHDCP version of the downstream link does not meet the security levelspecified by the security engine of the stream source. The HDCPdecryption block de-asserts the XOR EN signal for these filler symbols.

In the disclosed device and method, the HD HDCP version converterforwards all the sideband transactions (that is, AUX transactions)except for those for link management and for HDCP authentication and keyexchange. The DP HDCP version converter monitors the AUX command and a20-bit address field of the AUX transaction, and determines whether toforward or consume and reply to the AUX transaction. As the DP HDCPversion converter forwards all MST-related AUX transactions (forexample, MST capability discovery and topology discovery), insertion ofthe DP HDCP version converter does not add to the MST topology cascadelevels.

While the image display system 1 including the converter 3 has beendescribed above in detail, the foregoing description is in all aspectsillustrative and not restrictive. The above-mentioned variousmodifications may be used in combination unless any contradictionoccurs. It is understood that numerous modifications that have not beendescribed can be devised without departing from the scope of the presentinvention.

REFERENCE SIGNS LIST

-   3: DP HDCP version converter-   30: UFP receiver-   31: DFP transmitter

1. A DisplayPort (DP) High-bandwidth Digital Content Protection (HDCP)version converter that converts an HDCP content protection version frominput to output, the DP HDCP version converter comprising: a receiverreceiving a serial bit stream transmitted from an upstream device, anddecrypting link symbols of the received serial bit stream by use of adecryption unit; and a transmitter encrypting, by use of an encryptionunit, the link symbols decrypted by said receiver, and converting theencrypted link symbols into a serial bit stream and transmitting theserial bit stream to a downstream device, wherein said receiver and saidtransmitter have the same link configuration.
 2. The DP HDCP versionconverter according to claim 1, wherein said decryption unit forwardsthe decrypted link symbols to said encryption unit along with anencryption enable control signal and an XOR enable control signal, andasserts/de-asserts said XOR enable control signal based on whether thedecrypted link symbols need to be encrypted.
 3. The DP HDCP versionconverter according to claim 2, wherein said decryption unitasserts/de-asserts said XOR enable control signal based on a value in anEncryption Configuration Field (ECF) of a Multi Stream Transport (anMST) link frame.
 4. The DP HDCP version converter according to claim 2,wherein said decryption unit replaces link symbols of certain streamdata from said upstream device with filler symbols, and de-asserts saidXOR enable control signal for the filler symbols.
 5. The DP HDCP versionconverter according to claim 1, wherein said DP HDCP version converterforwards all sideband transactions from said upstream device except forthose for link management and for HDCP authentication and key exchangeto said downstream device.